The Ages of Gaia

A Biography of Our Living Earth

by James Lovelock

255 pages, paperback , W. W. Norton,
1995

The Ages of Gaia explains Lovelock's theory that the earth is a living
organism. The book describes how the living earth may work, today, and
in ages past, based on the latest research of Lovelock and others.

Praise for The Ages of Gaia

"This book describes a set of observations about the life of our planet which
may, one day, be recognized as one of the major discontinuities in human
thought. If Lovelock turns out to be as right in his view of things as
I believe he is, we will be viewing the Earth as a coherent system of
life, self-regulating and self-changing, a sort of immense living organism."--Lewis
Thomas, from the Foreword

Quotes from The Ages of Gaia

"Earth is indeed the best of all worlds for those who are adapted to
it. But the excellence of our planet takes on a different significance
in the light of the evidence that geochemists themselves have gathered.
Evidence that shows the Earth's crust, oceans, and air to be either directly
the product of living things or else massively modified by their presence.
Consider how the oxygen and nitrogen of the air come directly from plants
and microorganisms, and how the chalk and limestone rocks are the shells
of living things once floating in the sea. Life has not adapted to an
inert world determined by the dead hand of chemistry and physics. We live
in a world that has been built by our ancestors, ancient and modern, and
which is continuously maintained by all things alive today. Organisms
are adapting in a world whose material state is determined by the activities
of their neighbors; this means that changing the environment is part of
the game. . . . If, in the real world, the activity of an organism changes
its material environment to a more favorable state, and as a consequence
it leaves more progeny, then both the species, and the change will increase
until a new stable state is reached. On a local scale adaptation is a
means by which organisms can come to terms with unfavorable environments,
but on a planetary scale the coupling between life and its environment
is so tight that the tautologous notion of 'adaptation' is squeezed from
existence. The evolution of the rocks and the air and the evolution of
the biota are not to be separated."

. . .

"The simple model Daisyworld illustrated how Gaia might work. It pictured
an imaginary world that spun like the Earth as it circled and was warmed
by a star that was the identical twin of our own Sun. On this world, the
competition for territory between two species of daisies, one dark and
one light in color, led to the accurate regulation of planetary temperature
close to that comfortable for plants like daisies. No foresight, planning,
or purpose was invoked. Daisyworld is a theoretical view of a planet in
homeostasis. We can now begin to think of Gaia as a theory, something
rather more than the mere 'let's suppose' of an hypothesis.

"There is much more to Daisyworld than just the answer to a criticism.
I first made it for that purpose, but as it has developed I have found
it to be a source of insight and an answer to questions about theoretical
ecology and Darwinism, as well as to questions about Gaia. An important
property of the model is its docility and stability in mathematical terms.
As I continue to work with these models I find that the number of species,
and trophic levels, that can be accommodated appears to be limited only
by the speed and capacity of the computer used and by my patience. Whatever
the details, the inclusion of feedback from the environment appears to
stabilize the system of differential equations used to model the growth
and competition of the species."

. . .

"There is no way for us to survive without agriculture, but there seems
to be a vast difference between good and bad farming. Bad farming is probably
the greatest threat to Gaia's health. We use close to 75 percent of the
fertile land of the temperate and tropical regions for agriculture. To
my mind this is the largest and most irreversible geophysiological change
that we have made. Could we use this land to feed us and yet sustain its
climatic and chemical geophysiological roles? Could trees provide us with
our needs and still serve to keep the tropics wet with rain? Could our
crops serve to pump carbon dioxide as well as the natural ecosystems they
replace? It should be possible but not without a drastic change of heart
and habits."

"There is as yet no answer as to what proportion of the land of a region
can be developed as open farmland or forest without significantly perturbing
either the local or the global environment. It is like asking what proportion
of the skin can be burnt without causing death."

"The forests of the humid tropics act on a global scale by pumping vast
volumes of water back into the air (evapotranspiration); this has the
potential to affect climate locally by causing the condensation of clouds.
The white tops of the clouds reflect away the sunlight that otherwise
would heat and dry the region. The evaporation of water from the liquid
state absorbs a great deal of heat, and the climate of distant regions
outside the tropics is considerably warmed when damp tropical air masses
release their latent heat in the condensation of rain. The transfer of
nutrients and the products of weathering by the tropical rivers are obviously
part of their interconnection and must also have a global significance.

" If evapotranspiration, or the additions of the tropical rivers to the
oceans, is vital to the maintenance of the present planetary homeostasis,
then this suggests that its replacement with an agricultural surrogate
or a desert not only would deny these regions to their surviving inhabitants
but would threaten the rest of the system as well. We do not yet know;
we can only guess that tropical forest systems are vital for the world
ecology. It may be that they are like the temperate forests that seem
to be expendable without serious harm to the system was a whole; temperate
forests have suffered extensive destruction during glaciations as well
as during the recent expansion of agriculture."

. . .

"Gaia theory provokes a view of the Earth where:

Life is a planetary-scale phenomenon. On this scale it is near immortal
and has no need to reproduce.

There can be no partial occupation of a planet by living organisms.
It would be as impermanent as half an animal. The presence of sufficient
living organisms on a planet is needed for the regulation of the environment.
Where there is incomplete occupation, the ineluctable forces of physical
and chemical evolution would soon render it uninhabitable.

Our interpretation of Darwin's great vision is altered. Gaia draws
attention to the fallibility of the concept of adaptation. It is no
longer sufficient to say that 'organisms better adapted than others
are more likely to leave offspring.' It is necessary to add that the
growth of an organism affects its physical and chemical environment;
the evolution of the species and the evolution of the rocks, therefore,
are tightly coupled as a single, indivisible process.

Theoretical ecology is enlarged. By taking the species and their
physical environment together as a single system, we can, for the
first time, build ecological models that are mathematically stable
and yet include large numbers of competing species. In these models
increased diversity among the species leads to better regulation.

"We have at last a reason for our instinctive anger over the heedless
deletion of species; an answer to those who say it is mere sentimentality.
No longer do we have to justify the preservation of the rich variety of
species in natural ecosystems, like those of the humid tropical forests,
on the feeble humanist grounds that they might, for example, carry plants
with drugs that could cure human disease. Gaia theory makes us wonder
if they offer much more than this. Through their capacity to evaporate
vast volumes of water vapor through the surface of their leaves, trees
may serve to keep the ecosystems of the humid tropics and the planet cool
by providing a sunshade of white reflecting clouds. Their replacement
by cropland could precipitate a regional disaster with global consequences."